Recently, as the harmful effect of electromagnetic waves to the human body has been spotlighted, it has become a critical factor in the technology development of electric and electronic appliances to intercept or reduce the electromagnetic waves thereof. Particularly in the case of cellular phones of which there is nearly a one-to-one ratio with people, as they are used in contact with the human body (more specifically, the head), consumers rights organizations or national health agencies strictly regulate the radiation of electromagnetic waves thereof.
In order to evaluate the harmful effects of electromagnetic waves on the human body, relevant international or national agencies have presented standards of specific absorption rate (SAR) of electromagnetic waves, which is a measure of energy absorbed per unit mass in biological tissue when it is exposed to the electromagnetic waves.
It has been proposed as an SAR measurement technique that a phantom with built-in probes should be used to detect the intensity of electric fields absorbed therein from an electronic appliance such as a cellular phone.
With the conventional SAR measurement technique, the SAR is measured while continuously varying insertion positions of the probes to make surface distribution measurements, and the same process is again conducted to make minute volume distribution measurements. As such a process is repeated while varying the antenna state and the test position, it is very time consuming (for instance, three hours) to make a SAR for a single target product. Accordingly, the cellular phone manufacturers cannot make the SAR measurement with respect to all of the products, but are obliged to depend upon a sampling test. Furthermore, even in the case of the sampling test, sampling is difficult with respect to large numbers of products, thereby complicating the precise quality insurance.
Meanwhile, the phantom is not completed but is partially made such that only three sides thereof have outer skin while containing an imitation tissue gel therein. The probes are moved in the imitation tissue gel by a robot, and the SAR is measured while the one side of the phantom is in an opened state. Therefore, it is difficult to obtain a correct measurement value that can be approximated to reality so that the error range is enlarged. Furthermore, as the probes are repeatedly inserted into the imitation tissue and withdrawn therefrom, the imitation tissue gel is contaminated so it cannot be used for a long time. As a result, the high cost imitation tissue gel should be replaced, and such replacement is repeated frequently.
In order to solve the problem with the above-like probe usage technique, Korean Patent Publication No. 10-0600476 discloses a SAR measurement system and method capable of measuring the SAR within a short period of time by using an ultra-mini antenna and processors so as to obtain a precise measurement value that can be approximated to the practical SAR distribution.
However, with the SAR system and method disclosed in the Korean Patent Publication No. 10-0600476, whereas the whole SAR of the phantom can be measured in real time within a short period, it is difficult to precisely measure the SAR and to continuously make measurements with a predetermined temporal distance if the frequency is altered due to various usage environments of electronic products and the varied execution modes thereof.
Furthermore, Korean Patent No. 10-0692920 discloses a SAR system and method in which installs a memory unit is installed at a measurement module so as to continuously measure and store the SAR for a predetermined period of time, and to identify variations in the SAR by downloading and analyzing the stored data.
However, with the SAR system of the Patent No. 10-0692920, as the frequency signals received by the measurement module to make the measurement are used as driving power, it may be difficult to obtain desired driving power if the frequency signals to be measured are low in level. Accordingly, the measurement signals transmitted from the measurement module are weak, and a degree of amplification of several times should be conducted in order to receive and process the measurement signals. Furthermore, signal distortion may occur during the amplification process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.